Ink soil removal is a special problem in the laundry industry. Wiper towels and fabric sheeting which have been soiled with ink, i.e. where ink has penetrated the fabric, normally requires use of organic solvents such as mineral spirits, or mixed nonylphenol ethoxylate (NPE) and high caustic. Use of volatile solvents such as mineral spirits leads to fire hazards and contributes to poor air quality in laundry plants.
U.S. Pat. No. 5,340,493 describes a one-step ink-cleaning composition for removing inks from printer hard surfaces, e.g. rollers, metals, rubber surfaces while using woven polyester ink washing blankets which automatically remove ink from such ink transfer rollers and press parts. The composition uses tall oil fatty acid esters and nonionics but requires the use of mineral spirits.
U.S. Pat. No. 5,340,495; WO 95/18843 and EP 527 315 also describe similar one-step ink-cleaning compositions for removing inks from printer blankets as in the above '493 patent. The compositions employ fatty acid methyl esters, nonionic surfactants and possibly glycol solvents and volatile solvents like mineral spirits. No chelants are described in these references.
We have found that by employing a chelant and using an alkyl fatty acid ester in a pre-treatment step, improved ink removal results were found without the need for using volatile organic solvents.